Patent EP0026108A2 successfully refreshed from Google Patents.
EP0026108A2
Expired / Lapsed
EP
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Apparatus, circuit and method for compensating the dark current of photoelectric transducers
Assignee: Pfizer Inc
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Filing: 1980-09-24
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Granted: —
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Expires: 2000-09-24
Abstract
Abstract A sample and hold auto-zeroing feedback circuit (22) is utilized to drive the dark current of a solid state photodiode (10) to zero in the absence of incident light photons. The just previously attained compensation is then held during a subsequent quantitative measurement cycle when the photodiode is illuminated. A plurality of linear (24) and/or nonlinear (28) signal processing stages may also be included within the auto-zero compensation feedback loop such that their normal offset errors are also simultaneously compensated.
Inventors
- 👤 Ronald Frank Bax
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 19:21
CPC Classifications
G; G01; G01T; G01T1/00; G01T1/16; G01T1/20; G01T1/208; G01J; G01J1/00; G01J1/42; G01J1/44
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
147 words
Apparatus for reducing errors in photon measurements made with a photoelectric transducer having a variable offset component in its output electrical signal and which transducer is sometimes exposed to a source of photons, said apparatus comprising: a signal amplifier-circuit having an input connected to receive the electrical output signal of said photoelectric transducer, including said variable offset component and to provide a corresponding output, and a sample-and-hold feedback circuit connected to receive the output of said signal amplifier circuit and to sample same only during periods when said transducer is not exposed to said source of photons and to thereafter provide and maintain a respectively corresponding output feedback signal during periods when the transducer is exposed to the source of photons, said sample-and-hold feedback circuit having its output signal connected to control said signal amplifier circuit such that its output is compensated for said variable offset component.
Claim 2
Dependent Claim
147 words
Apparatus for reducing errors in photon measurements made with a photoelectric transducer having a variable offset component in its output electrical signal and which transducer is sometimes exposed to a source of photons, said apparatus comprising: a signal amplifier-circuit having an input connected to receive the electrical output signal of said photoelectric transducer, including said variable offset component and to provide a corresponding output, and a sample-and-hold feedback circuit connected to receive the output of said signal amplifier circuit and to sample same only during periods when said transducer is not exposed to said source of photons and to thereafter provide and maintain a respectively corresponding output feedback signal during periods when the transducer is exposed to the source of photons, said sample-and-hold feedback circuit having its output signal connected to control said signal amplifier circuit such that its output is compensated for said variable offset component.
Claim 3
Dependent Claim
41 words
Apparatus as in claim 1 wherein said signal amplifier comprises: a linear preamplifier stage having an input and an output, and an impedance isolation circuit connecting the output of the linear preamplifier stage to the input of the nonlinear amplifier stage.
Claim 4
Dependent Claim
46 words
Apparatus as in claim 1 or 2 wherein said sample-and-hold feedback circuit includes: a manually adjustable bias circuit connected to permit adjustment of the quiescent feedback signal to a value that approximately compensates said variable offset component at a predetermined operating condition of the photoelectric transducer.
Claim 5
Dependent Claim
77 words
Apparatus as in claim 2 wherein said linear preamplifier comprises: an operational amplifier having an input and an output, a pair of FETs (a) with one FET having a gate electrode connected to said photoelectric transducer, a source electrode connected to a degenerative feedback impedance and a drain electrode connected to the input of the operational amplifier and (b) with the other FET connected as a constant current load to the drain electrode of said one FET.
Claim 6
Independent Claim
107 words
A method of compensating for the temperature sensitive dark current component of the electrical signal of a photodiode, said method . comprising the steps of: generating an output electrical signal as a function of both the photodiode electrical signal and at least one compensation signal, generating said compensation signal as a function of said photodiode electrical signal during a time when the photodiode is dark so as to then substantially compensate for erroneous components thereof, maintaining the just previously attained value of said compensation signal when the photodiode is illuminated, and periodically repeating the above steps in synchronism with illumination of said photodiode during successive time intervals.
Claim 7
Independent Claim
107 words
A method of compensating for the temperature sensitive dark current component of the electrical signal of a photodiode, said method . comprising the steps of: generating an output electrical signal as a function of both the photodiode electrical signal and at least one compensation signal, generating said compensation signal as a function of said photodiode electrical signal during a time when the photodiode is dark so as to then substantially compensate for erroneous components thereof, maintaining the just previously attained value of said compensation signal when the photodiode is illuminated, and periodically repeating the above steps in synchronism with illumination of said photodiode during successive time intervals.
Claim 8
Dependent Claim
20 words
A method as in claim 5 wherein the first-mentioned said generating step comprises linear amplification followed by nonlinear logarithmic amplification.
Claim 9
Dependent Claim
34 words
A method as in claim 5 or 6 further comprising the step of: manually adjusting the quiescent value of said compensation signal so as to approximately compensate said output signal at predetermined operating conditions.
Claim 10
Dependent Claim
128 words
A light measuring photodiode circuit imposing substantially zero, said circuit comprising; a photodiode, an amplifier circuit having an input connected across said photodiode and having an offset input voltage drop at said input and thus appearing across said photodiode which can be controlled in magnitude to be substantially zero by a provided compensating input signal, said amplifier circuit also having an output providing a light measurement signal, and a sample-and-hold integrator circuit connected to sample the light measurement signal when the photodiode is not illuminated and to provide said compensating input signal at a magnitude so as to cause said offset input voltage to be substantially zero, said sample-.and-hold integrator circuit thereafter substantially maintaining said compensating input signal at its last attained value when the photodiode is illuminated.
Claim 11
Dependent Claim
128 words
A light measuring photodiode circuit imposing substantially zero, said circuit comprising; a photodiode, an amplifier circuit having an input connected across said photodiode and having an offset input voltage drop at said input and thus appearing across said photodiode which can be controlled in magnitude to be substantially zero by a provided compensating input signal, said amplifier circuit also having an output providing a light measurement signal, and a sample-and-hold integrator circuit connected to sample the light measurement signal when the photodiode is not illuminated and to provide said compensating input signal at a magnitude so as to cause said offset input voltage to be substantially zero, said sample-.and-hold integrator circuit thereafter substantially maintaining said compensating input signal at its last attained value when the photodiode is illuminated.
Claim 12
Dependent Claim
22 words
A light measuring photodiode circuit. as in claim 8 wherein said amplifier circuit comprises a nonlinear amplifier having a logarithmic-related transfer function.
References Cited (Backward Citations)
No citation records indexed.
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